Chemistry Formula
Molality Formula
Expresses concentration as moles per kilogram of solvent.
Formula Summary
Molality
Expresses concentration as moles per kilogram of solvent.
- Category
- Chemistry
- Equation
- m = n ÷ kg solvent
- Calculator
- Use Molality Calculator →
Equation
m = n ÷ kg solvent
Variables
- m = molality
- n = moles of solute
- kg solvent = solvent mass
How to Use This Formula
- Identify the known values from the problem statement.
- Convert all values into compatible units.
- Substitute the values into the equation and calculate the result.
- Check that the final answer has the correct unit and meaning.
Explanation
Molality describes the concentration of a solution by comparing the number of moles of solute to the mass of the solvent. Unlike molarity, it depends on solvent mass rather than solution volume.
Worked Example
A solution containing 2 moles of solute dissolved in 4 kg of solvent has a molality of 2 ÷ 4 = 0.5 m.
Common Mistakes
- Using solution volume instead of solvent mass.
- Forgetting to convert grams of solvent into kilograms.
- Confusing molality with molarity.
Applications
- Calculating concentration changes with temperature.
- Studying colligative properties of solutions.
- Advanced chemistry laboratory calculations.
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